This blog provides updated forecasts and comments on current weather or other topics

Friday, February 13, 2009

The Weekend

This is going to be a benign weekend with little weather action. We are in a pattern where the storms are deflected towards California and we get some weak cloud bands on their northern side. Today is a case in point....with the visible satellite picture showing the situation (see image). This morning the Cascades were really clear due to easterly flow sinking along the western slopes of the mountains (easterly flow causes drying of the air as it descends). There were also lots of mountain wave clouds. So in the lowlands there should be temps in the mid to upper 40s for the weekend, with partial sun. The mountains will get some occasional snow showers (mainly late Sunday, nothing heavy), with periods of intermittent sun. The snowpack is a stable hardpack now...and plenty icy. I was going to go cross country skiing...but may wait until better conditions occur. The rest of the week looks like more of the same. The silver lining? California will get the precipitation they really need.

I've been thinking about the drought question. I can't remember what year it was, but if my memory is right, one of Gov. Gregoire's first actions on taking office was to declare a drought. We had had a very dry rainy season until then, so it was justified, but then she was ridiculed because it started raining in February or March and continued to rain almost daily until June. Seems to me that a similar pattern also happened in 2000--I tried to start a garden in May, and the plants pretty much rotted in the ground because the skies never seemed to stop dripping. So, am I correct that a dry spell in early to mid-winter is not unknown? And, that the dry spell doesn't, in and of itself, predict the total rainfall for the October-June period? I'd love to hear from our weather experts on this question! Lyn in Lynnwood

If you want to peruse the monthly data for a particular year, go to http://www.wrcc.dri.edu/ and navigate down to the monthly totals data for whatever coop site is close to you. For instance, at Everett Jr. College, after the dry winter of 76-77 there followed a very wet May with just over 6" of rainfall--second only to May 1948. The trick to finding the data is to scroll down the left frame until you see Monthly Precipitation Listings Monthly Totals

You may have to surf around a few minutes to find the right spot. When you first start, click on the map of Washington State, then start to work you way down. Good luck!

Looking at the latest models... the 12z WRF, along with recent GFS models including todays 18z, it appears our split flow pattern will be continuing into at least maybe next weekend as the upper level jet is split in two. This will for the most part have any systems diving south toward our region, diving more toward California with better likely hood of rain down there. As for us, systems will be of the large scale upper level lows... weak lows...that when swinging down the west coast/ just off the west coast, will be close enough to give us maybe a few minor spotty showers/ sprinkles. However, we will remain mainly dry through this time with varying degrees of high/mid level cloudiness for the upcoming work week. The only likely places to get any form of precip up here will be the Olympics and Cascades. But even they will likely remain precip free for the most part. On the flip though, the 12zEURO and GEM model is wanting to drop a trough over us for late in the weekend and into early following week. So will see how things go.

It takes a bit of time to know the models, but you`ll eventually get a hang of it. Generally, the lower the 1000-500mb thicknesses, 850mb temps, and upper level heights are, the cooler the airmass will be.

As far as the long term, hard to tell just how cold it will be or if it will be cold at all. As for the snow chances, the GFS models have flirting around with the idea on and off, but I wouldn`t be putting anything on the back burner just yet since it`ll likely keep changing with every model run.

Tonights 00zGFS continues the idea of a split-flow type pattern through at least next weekend with systems mainly heading southeastward of the PNW and into California and leaving us mainly dry with varying degrees high/mid levels clouds for the work week. However, the GFS ''might'' be catching up to the GEM/EURO as the GFS now shows a trough/ frontal system coming through for the weekend. So we`ll see. The extended period looks a bit more wet and coolish and perhaps a bit more troughy, but at the same time, keeping the trend of a weakly split pattern. Also, the GFS is once again playing around with the idea in the extended range of some cold and snowy weather coming into the PNW as well as Montana. Thicknesses over us are shown to drop to near 504m with 850mb temps of -12 to near -14c along with northerly surface flow and 10m temps dropping to -10c. But as always, take long term for what it may be worth as the models will likely keep toying around with cold/snow over WA.

Looking at 6z/12zGFS, I see they are still pretty much wanting to keep the idea of a split flow type pattern that lasts into the weekend and maybe beyond that time frame. As mentioned before, this will keep us mainly dry with varying amounts of cloud cover, though cool with highs in the 40`s to maybe near 50. However, 00zEURO shows the idea of a trough or two dipping down over us for the weekend while both GEM and MRF show a wide, but weak and large scale low spinning close enough off the west coast to maybe spin up a few showers in our direction. On the flip side, the 12zGFS in the extended period shows us turning cool and showery and flirting with marginal snow chances over western WA around the 24th and into months end. So it looks like a continuation of current pattern with no real pattern change and or shift set in stone for the longer term period.